By announcing the US will limit it's security agreements to those who pay, Trump is basically announcing that the US is abdicating the role it gave itself after WWII.

But this comes at a cost. The US got a lot back for its security agreements. It had effective control over NATO command and it limited nuclear proliferation. It also bought it compliance from other powers on economic agreements. TPP was a case in point. It wasn’t just a free trade zone, it was an implicit agreement to contain China’s growing economic influence. The one thing Trump forgot to sell the US electorate when he sold him this “Let them pay!” line is that US influence will disappear accordingly. We already have seen this.. The US is now largely on the sidelines in Syria, reduced to largely being passive supporters of al-Qaeda as a bulwark against ISIS and supporting Kurdish forces against ISIS in Syria and Iraq. But this decline will accelerate. Germany and Japan will almost certainly develop nuclear arsenals.