I doubt any country other than Russia will attempt to target the actual sites of American missile defense installations. All other countries, including china, currently have few enough nuclear missile and warheads as it is. They can't afford to waste any on missile defense site. The chance of their warheads getting through to a missile defense site is probably no better than getting through to New York City. Yet a hit on a missile defense site will not incur heavy damage to US as a nation, while a hit on NYC will incur unacceptable pain upon the US. Yet hits at either place will invite American. Unclear retaliation.
So if it comes to lunching nuclear attacks, other countries might as well play for the maximum damage and pain by throwing all they have at high value targets like major population centers, rather than half assedly throw things at a missile defense site.
So if it comes to lunching nuclear attacks, other countries might as well play for the maximum damage and pain by throwing all they have at high value targets like major population centers, rather than half assedly throw things at a missile defense site.