At 100 km/h (low-end highway spreed), or 1,666 m/minute, or 27.7 m per second, a 2 second gap leaves approximately 56.6 m (185.6 feet) between cars. With the average car length being ~4.9 m (~16 feet), even the absolute worst driver can merge in a space ten times the size of the average car, assuming they're matching highway speed.
Most people have no actual concept of how long 2 seconds actually is or how much space it would leave in reality.