US Voltage > Touch Voltage > Fatal potentially
Touch voltage ie the level, which can penetrate the resistance of dry hands is 50V AC, US voltage is 120V AC, so could penetrate your skin and kill you, especially in one hand, out the other, frequency is also closer to your heart rhythm so more likely to induce fibrillation also than 240V at 50Hz AC.
120V DC is touch voltage, so you could touch 120V DC and potentially be ok, unless your hands are moist or sweaty where touch voltage drops to half dry hand touch voltage for both AC and DC.
Also many of those dedicated chargers especially on Ebay from China are VERY poorly built, (CE also stands for Chinese Export and many marks are forged, the Chinese have a triple C mark, however many of those are likely forged on ebay also) have under sized wiring and poorly connected wiring, which can and does melt, no internal fusing leading to damage to your laptop or your cars ECU (3 figure repair bill or more) and electrical systems or a fire in the event of a fault. Not withstanding that, many struggle to put out a steady voltage and current and many massively fluctuate, leading to laptop stability problems.
Best solution is an AC inverter with the OEM charger plugged in, bought from a reputable retailer, which as per the inverter in the article will shut off if the car battery drops too far (still allowing you to start the car), cut out if they overheat (something many ebay jobs never do) and produce steady voltage, which the charger for the laptop will even out further.