The US...No...we have no issue flame throwers in the inventory. Many other countries do and they ARE NOT banned under any international treaty. We do however have thermobaric weapons which are an updated version of the same thing and used extensively to clear caves in A-stan.
A thermobaric weapon, which includes the type known as a "fuel-air bomb", is an explosive weapon that produces a blast wave of a significantly longer duration than those produced by condensed explosives. This is useful in military applications where its longer duration increases the numbers of casualties and causes more damage to structures.
Thermobaric explosives rely on oxygen from the surrounding air, whereas most conventional explosives consist of a fuel-oxygen premix (for instance, gunpowder contains 15% fuel and 75% oxidizer). Thus, on a weight-for-weight basis they are significantly more energetic than normal condensed explosives. Their reliance on atmospheric oxygen makes them unsuitable for use underwater or in adverse weather, but they have significant advantages when deployed inside confined environments such as tunnels, caves, and bunkers.
The XM1060 40-mm grenade is a small-arms thermobaric device, which was delivered to U.S. forces in April 2003. In 2003, United States Marines used a thermobaric version of their Shoulder-launched Multipurpose Assault Weapon, called a Shoulder-Launched Multipurpose Assault Weapon-Novel Explosive (SMAW-NE), in the 2003 Invasion of Iraq. One team of Marines reported that they had destroyed a large one-story masonry type building with one round from 100 yards.
The 48-lb (22 kg) AGM-114N Hellfire Metal Augmented Charge introduced in 2003 in Iraq contains a thermobaric explosive fill, using fluoridated aluminium layered between the charge casing and a PBXN-112 explosive mixture. When the PBXN-112 detonates, the aluminium mixture is dispersed and rapidly burns. The resultant sustained high pressure is extremely effective against people and structures