Why is it the US is more prone into having tornadoes than the Philippines?

The main reason is that the Philippines are tropical while much of the U.S. has a temperate or subtropical climate. In a climate such as that of the U.S. there are greater temperature contrasts which leads to stronger thunderstorms. Particularly in the spring and early summer when the lower atmosphere is relatively war while the upper atmosphere is relatively cold the atmosphere becomes very unstable. This, accompanied by strong fronts and often a dry line can ignite violent thunderstorms capable of producing tornado, some of the very strong.

By contrast in a tropical area such as the Philippines the atmosphere is relatively warm at all levels pretty much year round resulting in a less unstable atmosphere. While some instability does occur and lead to thunderstorms, these storms are often generally strong enough to produce tornadoes.

Additionally, the U.S. is a much larger country than the Philippines and simply has more places for tornadoes to hit.