There is no such thing as transit visa to US. You would have to apply for a regular tourist visa in order to change flight at Los Angeles. All passengers would have to clear the US immigration and clear the customs as an entering traveller, regardless if you are connecting to a non-US destination or not. The US immigration and customs can be very long, 4 hours between flight might not be enough, especially if you catch up with the afternoon peak when all huge jets arriving from Pacific Asia. Three times I entered US through LAX, the inbound immigration procedure took at least 4-5 hours. If you are connecting between different airlines, you have to take all your bags to the domestic (including Canada) departure halls for re-check-in and undergoing the departure security procedure, which easily adding another 2 hours ordeal.
Transit (C) visas are nonimmigrant visas for persons traveling in immediate and continuous transit through the United States enroute to another country
There is no such thing as transit visa to US. You would have to apply for a regular tourist visa in order to change flight at Los Angeles. All passengers would have to clear the US immigration and clear the customs as an entering traveller, regardless if you are connecting to a non-US destination or not. The US immigration and customs can be very long, 4 hours between flight might not be enough, especially if you catch up with the afternoon peak when all huge jets arriving from Pacific Asia. Three times I entered US through LAX, the inbound immigration procedure took at least 4-5 hours. If you are connecting between different airlines, you have to take all your bags to the domestic (including Canada) departure halls for re-check-in and undergoing the departure security procedure, which easily adding another 2 hours ordeal.
No, you cannot do so without a visa. All passengers are required to clear the inbound immigration and custom upon arriving at the first port of entry as an incoming traveller, whether your final destination is US or not.
I know that the Consulate in Taipei does not issue transit visa, all C-visa requests were asked to apply the B1 visa in the past. You have to check with the US Consulate in Karachi to see if they would issue a transit visa.
