Confirmations are just a measure of computing power essentially. By saying a transaction needs 3 confirmations you are saying that you require 30 minutes of network hashing time before you call a transaction secure. For the same 30 minutes you'd need 12 Litecoin confirmations.
The chance of me solving 4 litecoim blocks is the same as me solving 1 bit coin block, assuming the same hash power and difficulty. In reality Litecoin is quite low in both, so is substantially easier to abuse in the real world.
No, confirmations are not just a measure of computing power. The difficulty of carrying out attacks with a sub-50% proportion of the total hash power increases exponentially with the number of confirmations, whereas requiring more work per confirmation only gives a linear increase. Satoshi's original whitepaper explains this.
The chance of solving 4 litecoin blocks is the same as solving 1 bitcoin block, sure.
But look at it this way. If bitcoin blocks were once a day, then if you had a few percent of the network power you would get 1 day = 1 confirmation ahead of your opponent all the time. But with bitcoin blocks every few minutes, you have an infinitessimal chance of getting 1 day = hundreds of confirmations ahead.
The distribution of timings is much wilder when you're only taking a couple samples. The longest confirmations in the world won't make 2-confirmation transactions completely safe, but 20 confirmations is pretty secure with any length.
The chance of me solving 4 litecoim blocks is the same as me solving 1 bit coin block, assuming the same hash power and difficulty. In reality Litecoin is quite low in both, so is substantially easier to abuse in the real world.