In the UK the domestic electrical system is fed from one phase and the neutral of the 230V supply. In modern houses, rightly or wronly, the earth connections of the three-pin sockets are connected to the neutral at the consumer unit (the junction box where the supply enters the house). In other words, the system is similar to what you have in the US except for the voltage being different and there being only one phase supplied to each house.
    If the power line or the antenna is struck directly by lightning there is little chance of the TV surviving. However, most surges are induced in the supply by nearby lightning strikes. In the EU, industrial equipment running from a 24v d.c. supply has to withstand surges of 1kV between the lines and 2kV from either of the lines to ground. If I remember rightly the requirements are 2kV and 4kV for 240V supplies but I'm not sure.
    I don't know whether equipment in the US is subject to similar requirements. If so, you probably have nothing to worry about. If not, you will still benefit from an ungrounded surge protector. The isolation provided between the supply and other connections (antenna, speakers etc.) to meet safety requirements will probably be so good that it will take an unusually large surge (line to ground)to do any damage.