Shapes U.S. military commitments
NATO membership obligates the United States to help defend 31 other countries, which influences where U.S. troops are stationed and how the Pentagon plans for war.
In plain English
When allies pledge to defend each other.
NATO is a club of countries, mostly in Europe plus the U.S. and Canada, that promise to defend each other if one is attacked.
Simple example
Sweden became NATO's 32nd member in March 2024, joining after Russia's 2022 invasion of Ukraine prompted it and Finland to end decades of military neutrality.
Why it matters
What the term actually changes.
Affects taxpayer costs
The U.S. accounts for roughly two-thirds of total NATO defense spending, making the alliance a significant factor in the federal defense budget debate.
How it works
The mechanics, in practice.
Collective decision-making
NATO operates by consensus, meaning all 32 members must agree on major decisions such as admitting new countries or launching joint military operations.
Spending commitments
Members pledged in 2014 to spend at least 2% of their GDP on defense; NATO reported 23 of 32 members met that target in 2024, up from 6 in 2021.
Related guide
Should the United States remain in NATO?
A look at the 75-year-old alliance, what membership costs and commits the U.S. to, and the case on each side.
Read the guide → Related issue brief
Should the United States remain in NATO?
Lawmakers and voters are debating whether continued U.S. membership in the 32-nation alliance still serves American interests.
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Should the United States remain in NATO?
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