You don't think the US protects the EU and largely acts as their military? What are you talking about?
Their military?
• Can EU command US forces?
• Can EU guarantee US rapid deployment in case of invasion?
• Are US forces patrolling any of the EU borders?
• Are US fighters patrolling the EU airspace? No (NATO fighters on rotation)
• Are US in position to assist in case of Russian aggression?
• Can EU request free military radars/defensive batteries/equipment/troops from US?
• Has EU ever invoked Article 5, or requested US military deployment in defense of offense of EU?
• Does EU not have their own military?
US is the biggest force in NATO, but it has never served anyone but US interests. It is in both US and EU interest to be in the alliance: US to project power, EU to have extra security and backing.
At no point US forces acted, or were expected to act as EU military.