The US outspends the next seven countries combined, and you don't think that's excessive? We should stop being a global police force, we can't afford it.
Keep in mind, "other factors" play into things here:
The United States is the 3rd most populous nation in the world, behind China (1.3 Billion), and India (1.2 Billion); it also is the 3rd largest country by area in the world, behind Russia and Canada(who is an ally).
We'll revisit some of those numbers shortly.
Before getting into the economic side, it should be pointed out that the military of a nation usually becomes larger when it has more to protect. What they have to protect is typically described both in terms of area and in terms of (value of) physical assets. Also there is something a ratio that nations attempt to maintain in terms of soldiers to general population.
So the more people you have in a country, the more people there should be in the military. So in terms of population alone, the US should have the 3rd largest standing military in terms of raw population numbers. With it only being beat out by China and India.
In terms of land area, again we should at least be in the top 3(and given Canada's population/location, why they're not is kind of understood; most of Canada is wilderness and not particularly hospitable to longer-term human habitation at any "advanced level" without needing outside support).
In terms of economic standing, we're supposed to be the largest. So our standing "head and shoulders above the rest" in military capabilities is hardly shocking. We have plenty of valid reasons for having a large and robust military force, as most of our country is NOT inhospitable wilderness. It just also happens that we have a high technology force, which is expensive to operate and maintain even if our raw numbers in terms of force size doesn't fully reflect the "other factors" in play, because of technology multipliers for the manpower we do have.
Now let us look at the economic side:
https://www.weforum.org/agenda/2018/04/the-worlds-biggest-economies-in-2018/According to the IMF sometime circa April of this year:
1) United States of America $20.4 Trillion
2) China $14 Trillion (4th largest by land(or
3rd depending on who you check and criteria used), largest by population(1.4B))
3) Japan $5.1 Trillion (61st by land area, 11th by population(127M))
4) Germany $4.2 Trillion (62nd by land area, 16th by population (82M))
5) United Kingdom $2.94 Trillion (78th by land area, 21st by population(66M))
6) France $2.93 Trillion (42nd by land area, 22nd by population(65M))
7) India $2.85 Trillion (7th by land area, 2nd largest by population(1.3B))

Italy $2.18 Trillion (71st by land area, 23rd by population(59M))
9) Brazil $2.14 Trillion (5th by land area, 5th by population(209M))
10) Canada $1.8 Trillion (2nd by land area, 38th by population(36M))
And China also is a special footnote because
nobody claims to know what China is spending on its military because of how their economy and military is structured, so trying to translate much of that into a meaningful and reliable number is a challenge unto itself. Everybody else's numbers are readily available for the most part however.
It should be noted however that China is building up/improving their military capabilities, India is doing the same, if only to keep pace with China because they have long-standing disputes with one another over territory. And Brazil likewise is expanding and improving its military capabilities as well. It is fairly new to being near the top of the food chain on at least some metrics at the least.
Edit: And it should also be noted that on that axis, all 3 of those "rising powers" China, India, and Brazil exist outside the direct purview of NATO, and while they present challenges to US interests, the European interests involved are much more mixed(and primarily either French or British in nature).
edit 2: It should also be noted that if you remove China from the list, it takes from Japan(#3) through to Italy(#8) to total the GDP of the United States of America. Which would be the combined economies of 6 rather large nations.