It’s old, but it’s definitely not easy. Even Tesla, one of the most brilliant physicists ever known, spent 40 years in vain in this research area. To effectively make a space shield that simultaneously intercepts thousands or even millions of incoming objects, planes or missiles alike, one must launch a high-density particle cloud to cover an entire region. Back then, they could only thought of electrons or protons. Today, photons may be cheaper. To effectively cover a region to intercept multiple warheads, a nuclear warhead may be launched into space such that its explosion will vaporize all objects within a certain sphere. To effectively cover a larger region, multiple warheads may be launched from a single missile to cover any desired geometric shape, just like fireworks. Artists know this the best. You can put a smile in the cloud just like that without any technical issue.
This is the problem, because competition is on if one is to take this route. To counter 3000 nuclear missiles, you will also need about 3000 nuclear missiles. Quantity matters. Is there a cheaper way to intercept more missiles simultaneously? Otherwise, clean hydrogen warheads are your best friends when you need the space shield. Both Russia and China are probably behind the U.S. by at least 40 years in this field. It seems also that their spies are not too effective yet. We will wait to see what they have to announce within the next 5-10 years.
Meanwhile, blessed are you who now are allies of the U.S.!
If you still want to worry, global stealth nuclear missiles are your best friends.