Freeloading? The USA spends massive amounts on its military exactly to maintain hegemony, European countries weren't going around the globe to fight pointless wars based on shaky (or completely fabricated) casus belli. There was no reason to spend a lot of tax money on military equipment, training, upkeep, just because. Russia's complete invasion of Ukraine shook Europe's defence outlook and created a reason to invest in it but that's it.
The USA providing security guarantees is not freeloading, it's USA's strategy to hegemony, it's how the USA has kept it...
Investing in defence without participating in wars (or to defend your hegemony) is just a waste of taxpayers' money, it's money that could go to healthcare, to education, or to any other improvement in quality of life of your citizens. I'm very glad that Europe hasn't been burning trillions of dollars on stuff just made to kill people.
