NASAs version of this is called StarTram, it's feasible but there are some major technical hurdles.

In the prototype stage, the launch velocity at the end of the gun would not be anywhere near the 10 km/s you would need to achieve orbit. But you could reach a sizable fraction, say 3 km/s. Becuase the velocity gained during rocket flight is not linear with mass, having that 3 km/s inital boost would reduce your overall rocket mass by like 80%. The rocket would clear the atmosphere and then fire its motor to gain a stable orbit.

We can achieve 3 km/s with current technology, it would require like a 100 km long maglev in a very low pressure tube, likely built on the side of a mountain. It could probably reduce space flight costs by a factor of 10 if completed.

Building the proposed goal of a human rated version capable of reaching near 10 km/s at the end point would be much more difficult. The tube would have to span over 1,000 km and I don't believe we have the technology yet to maintain the vacuum or supply enough power quickly enough to power it.

China is likely proposing to build a testbed system to start researching the concept. Probably on a larger scale than NASA has but nowhere near a complete system.

It's probably a high speed launch assist, not the entire source of escape velocity.

The Delta-V (change in velocity) to reach the ISS (400km) in Low Earth Orbit (LEO) is 9.4km/s. This is the absolute minimum so it doesn't include things like drag or other inefficiencies. Getting to space takes only about 1.4km/s, just about all the rest of that delta-v is used to accelerate the spaceship to 7.6km/s. This is about the minimum speed, altitude, and delta-v to get into orbit and stay there. Going much lower than the ISS will have your orbit decay too much to stay in orbit for more than weeks or months. I think it would take about 8000m/s to orbit right at 100km but your orbit would decay really quickly at that altitude, you would only get a few hours of orbiting.

I think I answered you below about why you can't to orbit using only a railgun.

Edit: Going from earth orbit to other places doesn't take as much delta-v as you might think. Going from earth orbit to lunar orbit only takes about 3km/s and going from earth orbit to mars orbit takes 5.7km/s.

It's true, China doesn't have rockets. The Tiangong space station was launched into space purely with the concussive force of Xi Jinping fucking your mom.